Soot is the main component of particulate matter (PM) generated in a combustion chamber of an internal combustion engine (particularly, a diesel engine). In order to accurately control the generation amount of such soot to thereby reduce the same, the generation amount of soot must be accurately estimated.
For example, an exhaust purifying apparatus for an internal combustion engine disclosed in Japanese Patent Application Laid-Open (kokai) No. 2004-44457 is configured to estimate the generation amount of PM, which changes in accordance with operating conditions of the engine, by making use of a map in which engine speed, accelerator opening, coolant temperature, etc. are used as arguments. When the PM generation amount is estimated, the amount of soot within the PM can be estimated.
Incidentally, in recent years, many studies have been performed on the mechanism of soot formation in a reaction process in which soot is generated from fuel. If the generation amount of soot can be estimated by means of a reaction model created on the basis of the soot formation mechanism, expectations are high that the generation amount of soot can be estimated more accurately.